Abstract 6699: CUE-102 Immuno-STATs for selective targeting and expansion of WT1-specific T cells for the treatment of HLA-A02+and/or HLA-A24+patients with WT1+malignancies

WT1 has been ranked first amongst 75 tumor associated antigens in an effort by the National Cancer Institute to prioritize cancer antigens for therapeutic targeting. Development of novel modalities to target WT1 provide a significant opportunity to address high unmet medical need in WT1-positive hematological and solid tumor malignancies, including AML, ovarian, endometrial, breast, lung, colorectal and pancreatic cancer. We have developed two novel fusion proteins, termed Immuno-STATs (Selective Targeting and Activation of T cells), that are comprised of either HLA-A*02 or HLA-A*24 molecules (human leukocyte antigen) presenting peptide epitopes derived from WT1. Each CUE-102 Immuno-STAT molecule also contains four copies of affinity-attenuated human interleukin-2 (IL-2), and an effector attenuated human immunoglobulin G (IgG1) Fc domain. We present here the biochemical characterization of these molecules and their bioactivity across a variety of in vitro and in vivo studies, demonstrating their ability to selectively expand, from a naive or pre-primed T cell repertoire, a polyfunctional population of WT1 peptide-specific CD8+ T cells capable of recognizing and responding to WT1 peptide-presenting target cells. Human peripheral blood mononuclear cells (PBMC) and WT1-specific CD8+ T cells were utilized to demonstrate cellular activity and specificity of CUE-102 Immuno-STATs. Repertoire analysis of WT1-specific T cells was done by single cell TCR sequencing. In vivo activity of CUE-102 molecules was assessed in HLA transgenic mice. CUE-102 Immuno-STATs presenting HLA-A*02 or A*24 specificities demonstrated selective binding and TCR triggering of WT1-specific CD8+ T cells. Signaling, cell-based assays and cytokine release studies confirmed significant functional attenuation of the IL-2 components of CUE-102. Primary stimulation of unprimed hPBMCs, or re-stimulation of hPBMCs after initial WT1 peptide stimulation, led to robust expansion of WT1-specific CD8+ T cells and demonstrated the ability of CUE-102 Immuno-STATs to stimulate and expand antigen-specific T cells from both a primed and pre-primed T cell repertoire. The expanded T cells exhibited a polyfunctional response upon challenge with WT1-presenting target cells, confirming that CUE-102 Immuno-STATs selectively expanded WT1-specific CD8+ T cells. The repertoire of the expanded cells, their polyfunctionality and ability to recognize and respond to WT1 peptide-presenting target cells suggest that CUE-102 Immuno-STATs have the potential to enhance anti-tumor immunity in patients with WT1-positive malignancies. Citation Format: Dharma Thapa, Alex Histed, Jonathan Soriano, Luke Witt, Zohra Merazga, Natasha Girgis, Miguel Moreta, Fulvio Diaz, Fan Zhao, Melissa Kemp, Paige Ruthardt, Anish Suri, Steve Quayle, John Ross, Saso Cemerski. CUE-102 Immuno-STATs for selective targeting and expansion of WT1-specific T cells for the treatment of HLA-A02+and/or HLA-A24+patients with WT1+ malignancies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6699.